Our Unit is interested in the molecular mechanisms underlying regulated patterns of gene expression in circadian time frames. During the current FY we have been focusing our studies on the contextual properties of circadian E-boxes. This work is important because the E-box is an extremely promiscuous DNA consensus element; thus, in order to understand how different signaling pathways can differentiate among different E-boxes, a systematic analysis of prototypic promoters is needed. The analysis of the vasopressin (AVP) promoter in this context led to the discovery of a putative novel transcription factor which appears to function as a co-activator of the circadian heterodimer BMAL/CLOCK. In a second project we are investigating the possibility that BMAL/CLOCK binding on specific promoters may act as a delaying device to postpone the cAMP mediated stimulation of other circadian genes that contain perfect E-Boxes at critical locations. A third project involves the mechanism of action of specific AP-1 complexes on clock controlled genes, which appear to be able to exert powerful suppression of BMAL/Clock mediated activation via an indirect pathway. Lastly, we have recently made the exciting observation of a thermogenesis-related gene displaying sex specific, tissue restricted and circadian expression in the rodent system. Its promoter is being analyzed to understand the mechanisms underlying such a complex pattern of expression.